Direct pushes to wmf/* branches disabled

While we were still getting set up with deployments from git/Gerrit, we have allowed deployers to push directly to the wmf/* branches using 'git push origin wmf/1.20wmf1'. This bypasses Gerrit completely, so there is no review (which is usually what we want), but also no e-mail notification, no IRC notification, and you can't find the commit hash or Change-Id in the Gerrit search (these are bad things).

So, as of 18:48 UTC today (about 30 minutes ago), this is no longer allowed: using 'git push' to push into the wmf/* branches will result in an error message ("Prohibited by Gerrit"). All commits in the wmf/* branches now have to go through Gerrit, which means you need to submit them with 'git review', and get someone to approve (+2) them before they are merged. The project owners group (for core this is the group of core reviewers ('mediawiki'), for extensions this is the extension owners) do NOT have the ability to +2 revisions in the wmf/* branches, this is reserved to the wmf-deployment group [1]. If you have deploy access, you should be in this group. If somehow you're not, get a Gerrit admin [2] to add you.

I have also updated the documentation accordingly [3]. If you have any questions, feel free to ask (on-list is preferred, but off-list is fine too).